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Prius Hybrid Maintenance Service Opportunities

The Toyota Prius contains plenty of new and possibly unfamiliar technology. But it's still a car, with routine maintenance opportunities that can be exploited by any savvy shop willing to take the time to learn what makes it tick.

Most Motor readers are searching for sensible service opportunities to increase their car counts and, therefore, their income. Predictably, many are eyeballing the higher-volume hybrid vehicles - probably with varying degrees of hope and fear, or a mixture of both emotions. With that in mind, here's a short primer on common maintenance opportunities on Toyota's second-generation Prius. "Second-gen" or "Gen-II" refers to the 2004 and newer Prius models, which happen to be the highest-volume hybrids on the streets today.

These cars are akin to other Toyotas: Earlier on, they just don't break down very often. Therefore, the bucks to be earned from them usually fall into the maintenance category. The good news is that informed, competent techs can do the work as easily as they do on any other vehicle. As you'll soon see, a little knowledge here goes a long way toward preventing problems and ensuring success.

What's more, these are not exactly inexpensive cars; typical Prius clientele tend to be people who understand the value of maintenance and will spend money on proper upkeep.

Before I proceed, remember two other things experience has taught us: First, an accurate vehicle history may be invaluable to solving the few oddball problems you encounter on the Prius. Second, a basic 12.00-volt battery powers the on-board computers as well as the most common electrical components. Never underestimate the importance of a good basic battery in these cars.

Familiarize Yourself

It's helpful to have experience starting and operating a second-gen Prius. If you don't, you're not alone by any means. Many techs just haven't had a chance to drive one. Anyway, check one out at your earliest convenience. Perhaps a sympathetic Prius owner in your neighborhood will show you or at least lend you the owner's manual. Maybe your buddy at the local Toyota dealership can teach you. Operating a Prius isn't difficult to learn, but it's certainly different from what most techs know about running a motor vehicle.

For example, the car may accelerate on the electric motor, on the gasoline engine or on a combination of both. This varies according to electrical load and driving style. But when the electric motor is propelling the car, the lack of traditional engine noise unnerves some techs. Likewise, you have to acclimate yourself to a car that usually shuts off the engine when it comes to a stop, and automatically restarts it whenever necessary. You see, the Prius' control system restarts the engine when it needs to recharge the high-voltage (HV) battery in the trunk of the car.

This brings us to the ready-to-drive mode, aptly named ready mode. Whether a Prius has the wireless Smart Key option or the basic key setup, the "key" actually is a rectangular fob. If it has the basic system, for example, slide this fob into a slot in the dashboard. Depress the brake pedal, push the POWER button once and the READY light should turn on. Now the car will move when you put it in gear, release the brakes and mash the accelerator pedal - even if its gasoline engine isn't running.

In case you missed it, look for the word READY on the instrument panel. (Toyota calls the instrument panel a combination meter, and it still contains the speedometer, odometer and warning lights.) Remember that whenever READY is illuminated, the car is in ready mode and the engine can restart whenever the control system demands it.

You may have heard wild stories about the second-gen Prius, including alleged high-voltage high jinks and engines that restart without warning. Suppose a Prius has been running okay and then comes into your bay for maintenance work. First of all, these common services don't involve the high-voltage area of the car at all. You don't have to disable the high-voltage system to do routine maintenance.

Second, the gasoline engine actually can restart in the middle of a service job. But that's possible only if you leave the car in ready mode. Proper procedure requires shutting off ready mode before you do any kind of service.

Make the following steps standard procedure and don't deviate from them: First, pull the car into the bay; apply the parking brake, set up the lift, release the hood and rear hatch, etc. Then write the odometer reading and/or other relevant information on the work order or a notepad right away. Hand it to a service writer or put it in your toolbox. Now the service writer has no legitimate reason to return and power up the car again.

Next, disable ready mode by simply shutting off the car. In other words, if the READY light is still illuminated, push the POWER button one push at a time until the light goes out. When it goes out, the rest of the instrument panel display also turns off. Once READY is shut off, the engine cannot restart unless someone has climbed in the car and played with the controls. So another part of your new shop procedure is that no one messes with Prius controls after a tech has turned out the READY light.

Oil's Well That Runs Well

Believe it or not, botched oil changes have been a headache on both the first- and second-generation Prius. Toyota actually issued bulletins about these mistakes. Furthermore, specialists I know who have serviced the Prius since its introduction in 2001 said they've seen their share of trouble caused by shade-tree mechanics as well as careless technicians. These oil-related problems remind us just how precisely these vehicles are designed and calibrated.

For instance, some people create excessive parasitic drag inside the engine by installing heavier viscosity oil. (For your information, Toyota recommends 5W-30 viscosity oil for all Prius models from 2001 to present.) This additional drag reduces both fuel economy and cranking speed. The correct cranking speed is so critical that if a Prius engine doesn't restart within the specified time, it triggers DTC P3191. Technically, this code means "Engine Does Not Start." But in this instance, it really means that although the engine restarted, it didn't restart quickly enough.

Here's just one example of the aggravation thicker viscosity oil causes. A Prius owner changed oil and installed 10W-40. Later, his car began setting the P3191 code, but only when the temperature dropped below about 32°F! He never thought to mention the oil change or the heavier oil. Meanwhile, the techs diagnosing the car never sought the vehicle history, either.

Overfilling the Prius crankcase is another basic mistake that increases drag, reduces fuel economy and may trigger the no-start DTC. By the book, an oil and filter change on this engine should require barely four quarts of oil. Considering the potential consequences, it's worth taking extra care to be sure you don't overfill it. For instance, some techs routinely pour in three quarts. Then they warm up the engine and top off the crankcase a wee bit at a time, finishing up with the oil level a little bit below the upper mark on the dipstick. They argue that it's smarter to be a little below full than over it. The approach has worked well for them.

(Reportedly, there have been cases where thicker oil and/or overfilling have actually prevented a Prius engine from restarting. Forewarned is forearmed!)

The Prius engine is an Atkinson cycle design. Its unusual valve timing allows reversion to occur, leaving some residue inside the intake manifold. This is normal. However, an overfilled crankcase can leave puddles of motor oil inside the intake manifold. Sources said that experience is the only way to quickly distinguish the difference between normal residue and abnormal puddles of oil here.

You could change the oil and filter, clear any trouble codes and then try driving the car aggressively to purge the oil puddles. You could also perform an induction/intake cleaning service with a kit such as those offered by BG Products (www.bgprod.com), Run-Rite (www.Run-Rite.com) and others. While you're at it, check the throttle blade and housing for varnish and coking. Then carefully clean them as needed. Use spray chemicals sparingly here so you don't force any chemical into the throttle motor assembly.

Such services as throttle cleaning, induction cleaning and decarbonizing the valves and combustion chambers may become more valuable simply because the Prius engine just doesn't run as frequently or as hard as a conventional engine does.

Regardless of what you're doing, be extremely careful to keep excessive amounts of liquids out of this engine's intake and cylinders. Unwanted liquids have been known to readily bend connecting rods in this engine.

Activating Inspection Mode

Other aspects of normal Prius operation affect our work out in the bays. For example, there are times when we want an engine to idle uninterrupted (for lack of a better description) for emissions testing, engine or ignition analysis, warm-up and so forth. When the car is in Park, this engine may idle, but only as long as needed to recharge the HV battery, then it shuts off. Although the engine does idle in Neutral, the system doesn't recharge the HV battery in Neutral.

The simple solution here is to activate Inspection Mode. This lets the engine idle normally and allows the system to recharge the HV battery as needed. To activate Inspection Mode on the Prius, the following steps must be completed within 60 seconds:

1. Keep your foot off the brake pedal. Then "power up" the car by pressing the POWER button twice.

2. Next, floor the gas pedal and fully release it twice.

3. Depress the brake pedal and keep it depressed with your left foot for the rest of this procedure.

4. Shift into Neutral, then floor the gas pedal and fully release it twice.

5. Shift back into Park, then floor the gas pedal and fully release it twice.

6. Now the HV warning light on the multi-information display (TV-like screen) should flash. This warning light has the silhouette of a car with an exclamation point (!) on it.

7. Push the POWER button. The engine should start and continue idling at about 1000 rpm.

8. Press the POWER button one more time to shut off the engine. This last step also deactivates Inspection Mode.

The important thing to remember here: Never, ever road-test a Prius while it's still in Inspection Mode!

Transaxle Fluid Service

The only mention of Prius transaxle service that I found was a 30,000-mile interval for "severe-duty" driving on 2004-06 models. There's no recommended interval for the newer cars. All I'll say here is that Prius transaxle assemblies are not cheap. Some Toyota specialists recommend changing the fluid at least every 60,000 miles. The specified lubricant is Toyota's WS (World Standard) fluid (Part No. 00289-ATFWS or its equivalent if an equivalent exists).

Note that the socket-head (Allen-head) drain plug on the bottom of the transaxle is the correct one for draining the transaxle. If you trace a line straight upward from this transaxle plug, you'll find another socket-head plug in the side of the transaxle; that's the fill plug. Slowly refill the transaxle through this fill hole until some fluid just begins to dribble out. Then reinstall the socket-head fill plug.

Engine Coolant Services

Cooling system service on the second-gen Prius is unusual for two reasons. First, its traditional cooling system includes a heat storage tank and a dedicated pump. The storage tank is an insulated aluminum unit that's hidden inside the left front fender at the corner of the car. It can store heated coolant - approximately 176°F - for as long as three days. When the customer starts the car, a pump mounted next to the tank circulates this heated coolant in order to preheat the cold engine. Preheating the engine reduces hydrocarbon emissions. Note that at any given time, the coolant inside that tank is still hot.

Second, the Prius has a separate, mini cooling system that serves both the inverter and transaxle. For now, I'll just say the inverter is a very, very busy electrical component on top of the engine that gets so hot that it needs its own cooling system. Toyota recommends its own, premixed Super Long-Life Coolant for both cooling systems.

The first step in servicing the traditional side of the cooling system is to disable the heat storage tank pump. Look up at the storage tank and locate the gray two-wire connector. Unplug this connector from the pump on the side of the aluminum storage tank.

Next, you have to open three drain cocks under the car in order to drain the system, so wearing eye protection ain't a bad idea. Also, you can minimize the mess in your bay by connecting a temporary drain hose to each drain cock; hose with approximately 3/8-in. I.D. should work fine. Then route the three hoses into the same drain container.

One drain cock is very easy to reach because it's right on the bottom of the heat storage tank; it has a yellow, wing-shaped "handle." The second drain cock is more difficult to see because it's buried on the driver side of the radiator. It also has a yellow handle on it. The third drain valve is way up on the rear of the engine block, toward the passenger side.

You may already have a "vacuum-fill" device. If you don't, then one attempt at refilling a Prius inverter cooling system may convince you to get this kind of tool because it'll save so much time.

Refill the system with coolant, install the radiator cap and reconnect the gray connector to the storage tank pump. Connect a scan tool to the car and turn the ignition on by pressing the POWER button twice (amber light on the button illuminated). Use the appropriate scan tool command to turn on the storage tank pump. Keep checking coolant level and add a little coolant at a time as needed. Remember to turn on the storage tank pump every time you add coolant. If you forget to run the pump or have air in the system, it will cause a coolant-related trouble code.

The inverter's coolant reservoir is right on top of the engine next to the inverter. Remove the reservoir cap and then pull the drain plug on the bottom of the transaxle. It's a 24mm hex; don't confuse it with the socket-head transaxle fluid drain plug. Using a vacuum-fill tool such as the Airlift will save more time and aggravation refilling this inverter system than you can imagine. Yes, you can fill it the traditional way and use the bleeder on the top front of the engine to bleed the system. But manually bleeding this system the old-fashioned way can take a very long time!

Anyway, refill the inverter cooling system with an appropriate refill tool, then push the POWER button until the READY light is on. This will turn on the inverter system's electric coolant pump. Let the pump run for several minutes and check the coolant level in the reservoir on top of the engine. When there's no air in the system, the pump runs quieter and causes a noticeable swirl or turbulence inside the reservoir. Carefully top off the coolant in the inverter system reservoir as needed.